NMES: Neuromuscular Electrical Stimulation Flashcards
NMES
Neuromuscular Electrical Stimulation:
Application of an electrical current to result in a tetanic contraction (a smooth transition from relaxation to contraction)
Muscle must be innervated for carry-over to occur
Will release endorphins similar to TENS…so may affect pain also.
Sometimes referred to as estim
clinical applications:
- Strengthen or prevent disuse atrophy (Medicare Language = strengthening)
a. Beneficial if need to isolate a muscle
i. If a particular muscle is not working adequately (i.e. trace muscle strength)
b. Electrical stimulation vs. therapeutic exercise
i. Same theory: isometric 6 second hold to strengthen: 10 rep 1 – 3 sets: NO LONGER
ii. Best if use active motion with estim (NMES) - Increase AROM
a. Orthopedic settings: assist with pull through in occurrence of tendon adhesions
i. Not painful: patient not strong enough to pull through with own strength
b. Inhibition of spacticity or muscle spasms
i. Stimulate antagonist of an high tone muscle to induce reduced tone
ii. Ie. Fisted hand after stroke or head injury: could stim to open for hygiene or to gain access to positioning and to provide ROM to prevent contracture/pain - Muscle Re-education
a. Gives sensory feedback and helps motor learning
i. Tendon transfers, muscle imbalance - Orthotic Substitution – FES: (functional electrical stimulation)
a. Shoulder subluxation
b. Ambulation: ie. Christopher Reeves - Edema Control
a. By-product of any active muscle contraction
Denervated Muscle
This is a grey area: Different theories that contradict themselves:
o On dennervated muscles you could be preventing muscle deterioration/atrophy
o If the nerve is regenerating you may over stimulate and slow or stop nerve growth
duty cycle
Duty Cycle: On/Off Cycle.
Requires at least a 1:2 ratio of on to off time.
Some research suggests 1:5 may prevent fatigue and is better for strengthening
Ramp Up time(rise time): the time it takes for the electrical current to reach the full rate Ramp down (fall time): the time it takes for the electrical current to return to rest. Generally: 2 seconds to ramp up…..hold for a 6 second isometric hold….and 2 seconds to ramp down = 10 seconds On
So if you choose 10 seconds on you would need 20 seconds off
If you choose 15 seconds on you would need 30 seconds off.
Affects fatigue. If patient fatigues then increase off time
Rate (frequency)
this is measured as the current in pulses per second (pps).
25 pps – allows for stimulation only
35 pps – allows for contraction of small muscles
50 pps – allows for contraction of larger muscles and is at times used when little response is seen at 35 pps.
wave form
Wave Form:
Symmetrical: this is the type of wave form that results in a more comfortable response as the two wave phases cancel each other out and there is no over loading of current. We choose this first since it is more comfortable
Assymetrical: This wave form is less comfortable and creates a build-up of current in the muscle. We use this wave form when we are unable to successfully elicit a contraction from symmetrical. It creates the greatest nerve excitation under the negative electrode.
Cycling:
Alternating or Synchoronous. This relates to the number of separate currents you have occurring during a treatment and when they occur. There are two lead wires each going to a set of two electrodes.
Synchronous:
• used at a time when you want to have both leads work at the same time.
Ie. Two electrodes on vastus medialis and two on vastus lateralis. You want them to stimulate at
same time to activate this larger muscle group.
Alternating:
• used when you want the electrodes to alternate
Ie. Lead 1 is connected to two electrodes on the flexors and lead two to electrodes on the extensors. The current would alternate between the two allowing for alternating flexion and extension.
• Also used when you are using only one lead to one group of muscles (this is the most common for our purposes)
Pulse width
this is the length of the individual wave form. For UE musculature we always set this at 300 miliseconds as this is most comfortable and effective.
Time:
Generally you want the client to perform 10 -12 reps. You may repeat up to three times with a several minute break in between. This is a math problem looking at the time to compete a cycle of on/off multiplied by the number of reps.
Electrode Size and Placement
- Use two electrodes (or multiples of two) : One over the motor point
- Size is based on maximizing muscle coverage while minimizing overflow into other muscles.
Negative vs. Positive
• If symmetrical waveform: no need to pay attention to polarity
• If assymetrical waveform: recommend negative at motor point (limited evidence; heresay)
polarity
Bipolar:
• Use same size electrode over muscle parallel to fiber at each end of the muscle belly for most comfort
Monopolar:
• use smaller electrode over motor point you want to isolate and a larger electrode elsewhere as a dispersive electrode. (ie. Palmaris longus transposition to thumb)
• Used to get a stronger and more specific response but may be less comfortable
• This will increase the current density to the motor point so may need less amplitude
Other things to think about:
- Rate and duty cycle will affect the quality and strength of the muscle contraction and rate of fatigue
- Amplitude will affect comfort level and determine the magnitude of the sensory motor response
- Fatigue will occur +> Stop if it does
- If biting sensation or burning sensation occurs, replace electrodes
- Make sure full contact with skin
- If using for home use check understanding, compliance, and tolerance
Precautions and Contraindications
Follows standard electrical modality precautions and remember:
• Any time active exercise is contraindicated, NMES is contraindicated
